Broadcasting unions have vowed to ballot for strike action at the BBC as soon as this afternoon after director general Mark Thompson yesterday outlined his vision for a "smaller BBC, but one which packs a bigger punch".

Confirming 2,500 job losses, and further angering unions by promising to axe them "as fast as possible", Mr Thompson made a personal plea to staff.

In a speech broadcast to the BBC's 18,000-strong workforce, he said he "loved the BBC too much to see it drift into irrelevance" and argued radical surgery was necessary to safeguard its future.

In light of a below-inflation licence fee rise that averages 1.4% over the next five years once digital switchover costs are taken into account, Mr Thompson said the corporation would reduce the number of programmes it makes by a 10th, cutting commissioning budgets by £100m, and produce fewer websites.

He confirmed the widely leaked figure of 1,800 redundancies, with the rest due to natural wastage and redeployment.

Broadcasting union Bectu and the National Union of Journalists said staff were outraged and felt they were "paying for management's incompetence with their jobs". Unless the BBC abandons plans to send out letters trawling for voluntary redundancies by midday today, they will call an immediate strike ballot.

"We were expecting redundancies as a result of the poor licence fee settlement, but this is far greater than we expected, or is required," said Bectu general secretary, Gerry Morrissey. "We are concerned that the salami slicing proposed by management will damage quality as well as put unreasonable demands on staff."

The factual department, home to shows such as Top Gear and Timewatch, and BBC News, where there will be a new integrated newsroom combining provision for TV, radio and the web, will face the biggest cuts.

Jeremy Dear, general secretary of the National Union of Journalists, said: "We have been given barely 20 minutes to scrutinise the plans. There is a lack of information and a lack of goodwill from the BBC. They must withdraw these plans, agree a framework for negotiations or face the potential of strike action."

In all, production arm BBC Vision will make net redundancies of between 640 and 660 people over the next six years, around a quarter of the total, with an estimated 390 from the factual arm.

Jana Bennett, the director of BBC Vision, said "middling" programmes would be axed, with resources diverted to flagship programmes such as Planet Earth and Andrew Marr's History of Britain, and strands such as Panorama, The One Show and Horizon. Light factual and late night programming will be cut.

Pressed for an example of the type of programme that would no longer be commissioned, she named Comedy Connections, a late-night BBC1 series devoted to comedy legends.

She said strands such as Horizon, Storyville and Timewatch would be saved but there would be more "narrative repeats" outside peak time BBC1, with shows being stretched across more platforms and shared between BBC2 and BBC4.

Mr Thompson said cutting £100m from the annual commissioning budget would have "a much higher impact" than closing BBC3 or BBC4. "Nowhere in the world are people closing down networks - you want as much shelf space as possible," he said.

He defended the large salaries earned by a "small number of absolutely widely loved, admired, enjoyed talent" after criticism of the £18m three-year pay deal for Jonathan Ross, but admitted talent costs would come under increased scrutiny.

Those present at his meeting with 150 key presenters dismissed suggestions that it had turned into open revolt. John Humphrys, the presenter of the Today programme who has argued for the closure of BBC3 to safeguard news provision, said it was "remarkably congenial".

BBC News will lose up to 490 posts, a net reduction of up to 370, as staff are integrated into a converged newsroom combining TV, radio and online.

The deputy director general, Mark Byford, said it was vital that the BBC's journalism moved with the times, pointing to statistics showing the reach of BBC News on television was down by 5% since 2001 and online news up by 12%. He announced new broadband portals called MyNewsNow and MyLocalNow that will offer a personalised take on the day's news.

The figures

The net redundancies across the BBC over the next five to six years

Vision 640-660

Nations and regions 510-550

News 355-370

Future media and tech 120-130

Audio & music 65-75

Professional services up to 75

Sport up to 20

Total c 1,800

Redundancies region by region

Scotland 155-165

Wales 145-55

English regions 130-150

Northern Ireland 75-85

Posts being closed region by region

Scotland 225-240

Wales 220-235

English regions 370-390

Northern Ireland 100-110

Net redundancies within the new integrated BBC newsroom, after reinvestment

Editor grade posts 40%

Assistant editors 30%

Senior producers 20%

Producers 5%

A total of 113 posts will be lost in the newsroom in the first two years, with 180 to 190 posts to go over five years. The BBC News website will lose its political correspondent.